Lamp base



March 1969 a. KOPELMAN ETAL 3,431,540

LAMP BASE Filed Jan. 30, 1968 INVENTORS BERNARD KOPELMAN ROBERT M. SHIMER BY g a raw ATIQRNEYH nited States 3,431,540 LAMP BASE Bernard Kopelman, Salem, and Robert M. Shimer, South Hamilton, Mass., assignors to Sylvania Electric Products Inc., a corporation of Delaware Filed Jan. 30, 1968, Ser. No. 701,625

US. Cl. 339112 Int. Cl. H011- 13/46; H013 7/24 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field the invention This invention relates to high current lamps having tungsten filaments enclosed in sealed envelopes, the latter being of fused quartz or other suitable glass. Such devices generally contain a halogen, such as iodine or bromine, and are usually called halogen-quartz lamps. They operate on a regenerative cycle, initiated when a tungsten halide is produced and chemically combines with the particles evaporated from the incandescing tungsten filament. Subsequent thermal decomposition of this compound replaces the tungsten particles on the filament. More particularly, this invention concerns an improved heat dissipating means integral with the base of the lamp, and adapted to be operational with high current loadings of the type described above.

DESCRIPTION OF THE PRIOR ART Briefly, in the fabrication of quartz-halogen lamps the important sending operation includes wafer-thin strips of molybdenum as current conductors in the seal area. These strips are welded between a lead-in wire and a filament-support wire. This assembly is fitted into a quartz tubular envelope and after softening of the quartz, a mechanical sealing die is pressed upon the softened portion. This sealing operation pinches the area where the molybdenum strip bridges the lead-in wires and provides a vacuum-tight seal.

The problem encountered with the use of molybdenum foil as a seal conductor in high wattage lamps are many. But the most critical is that, when current is passed through the foil a continuous heat build-up occurs because of the low thermal conductivity of the quartz.

In the basing of these high wattage lamps, certain advancements have been made. The press-seal portion of the lamp is normally held in many fashions. Basically a ceramic or metal cam is disposed about the press-seal and held in place by a basing cement; for example, Saueriesen cement, Duco or the equivalent. .This cement completely covers the press-seal area. When the heat builds up because of the current passing through the molybdenum foil, it is entrapped by the cement which acts as an insulator and accentuates the problem of the poor conductivity of the glass. The seal then breaks quite frequently.

The seals frequently attain temperatures of 350 C. or better and the foil rapidly deteriorates. Therefore, these high wattage lamps have to be operated at seal temperatures of less than about 350 C. This limitation can restrict the freedom of reflector and fixture designs in the expanding lighting field.

3,431,546. Patented Mar. 4, 1969 SUMMARY OF THE INVENTION In the present invention we have designed a base arrangement which reduces the possibility of breakage in the seal area. An enlarged, outer metal cannister is disposed about the press-seal area and a pair of contact pins extend from the lower end. The contact pins are welded to the lead-in wires of the lamp. A heat sink having a saddlelike shape and with angled fins at the ends is disposed over the press-seal and inside the metal cannister. The fiat sides of the saddle lie firmly against the flat portions of the seal of the lamp, and from each end of the flat sides the outwardly extending fins are formed. The distance between the tips of the fins is equal to the inner dimensions of the metal cannister. Therefore, when the saddle is in place over the seal and the lamp and saddle are placed within the cannister, the angled fins contact the inner wall of the cannister and form a wedge area at each end. A cement is applied in this wedge area leaving the flat portion area adjacent the seal free of cement. The bottom of the lamp is also free of cement which provides an unrestricted path for air currents over the seal portion of the lamp. Hence, radiant heat generated in the flat seal is passed into the fiat portion of the saddle, and then through the fins into the walls of the cannister. The heat carried from the flat portion of the lamp to the outer metal cannister prevents injury to the seal during normal operation.

Other objects and further features of the invention will be readily apparent from the following description and drawings in which:

FIG. 1 is a perspective in an exploded arrangement showing in particular the particular components of the invention.

FIG. 2 is a perspective view of the lamp arrangement in completed form.

FIG. 3 is a sectional view taken on the line 33 of FIG. 2.

FIG. 4 is an enlarged cross section through the base area showing in particular the path for convection of air currents.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the lamp and socket arrangement of our invention comprises a hermetically sealed vitreous envelope 10 which contains a coiled-coil tungsten filament 12 connected at its ends to respective lead-in conductors comprising inner and outer portions 14 and 16 respectively. The inner and outer, lead-in wires are separated in the seal area by molybdenum foil strips 18 which are hermetically sealed in spaced-apart relation in a compressed protruding seal portion 20, formed at one end of the envelope. The outer portions 16 of the lead-in conductors extend beyond this press-seal area 20.

The particular lamp shown is of well-known iodinecycle type where during lamp operation a small amount of iodine vapor functions as a getter to combine with tungsten that is vaporized from the filament 12 onto the envelope wall to thereby form a tungsten iodide which migrates back to the vicinity of the filament, where it then redeposits tungsten onto the filament and releases iodine for continuation of the cycle.

As viewed in FIG. 1 the lamp and base components are illustrated in a pre-assembled relationship. The main elements of the base structure are: a saddle-like metal heat sink 21 tubular metal contact prongs 22, a ceramic contact holder 24 and a rectangular-shaped metal cannister 26.

Each of the contact prongs 22 is provided with an enlarged node 28 midway on its length which node is utilized as a limiting stop when the prongs are inserted into the bottom of the contact holder 24. When in place in the holder, the nodes 28 will abut against a restricted portion and the upper ends of the prongs 22 are flared thereby locking them in place.

This pre-assembled contact holder with the prongs 22 in place is then positioned within the cannister and a reduced portion 34 of the holder 24 will be allowed to pass through the bottom area of the metal cannister.

The heat sink arrangement 21 is seen clearly in FIG. 1 as an inverted saddle-like component. The flat portions 40 of the sink are joined together by curved segments 42 separated by a relief area 44. Each end of the fiat portions are provided with angled fins 46 extending outwardly from the fiat portions.

Prior to inserting the lamp 10 into the cannister 26, the saddle 21 is slipped over the press-seal area 20 of the lamp. The fiat portions 40 of the saddle firmly in contact with the flat portion of the seal.

The lamp 10 with the saddle attached. is then positioned within the cannister 26 where the outer lead-in wires 16 of the lamp are positioned within the metal prongs 22 clearly seen in FIG. 4. A suitable soldering or welding operation is then made to the lower ends of the prongs 22, fusing the lead-in Wires to. the prongs 22.

Referring to FIG. 2 where a completed lamp assembly is shown, and showing in particular the fins 46 angled out to bear against the sides of the cannister. In their angled position, the fins 46 define a restricted area 48 that is filled with conventional cement 50. In reference to FIG. 3 the angled fins are shown more clearly defining two distinct areas, the restricted area 48 filled with cement and the clear larger area 52.

In the finished basing of the lamp a complete path for air travel around the flat portion of the seal area is formed. As seen in FIG. 4 the lower end of the pressseal portion of the lamp does not seat on the ceramic holder 24 but is spaced away from it to provide a circulating path for air currents.

With the particular arrangement shown and described above, a cooler lamp seal area is attained. I-Ieat generated in the seal area is dissipated by the combination of the heat sink saddle 21 and the absence of cement adjacent the flat portion of the seal.

It is apparent that other changes and modifications may be made within the scope of the instant invention but it is our intent, however, to. be limited only by the scope of the appended claims.

We claim:

1. An electrical lamp comprising:

a sealed envelope of vitreous material having a pressseal at one end thereof;

a pair of lead-in wires hermetically sealed through said press-seal in spaced apart relationship to one another and extending beyond said press-seal;

said lead-in wires being connected at their inner ends to a filament;

a metal cannister disposed about said press-seal and having a slightly larger cross-section than said pressseal;

a heat sink means abutting against said press-seal, the ends of said heat sink means extending to the walls of said cannister, thereby holding said cannister and defining areas of free space.

2. The lamp according to claim 1 wherein basing cement is disposed in at least one of said areas of free space to provide for rigid basing.

3. The lamp according to claim 1 wherein said heat sink has oppositely disposed flat surfaces having angled fins on each horizontal edge thereof, said angle fins, when positioned within said cannister defining a restricted area for the application of basing cement and a larger area free of cement adjacent said press-seal potting of said lamp.

4. The lamp acording to claim 3 wherein said oppositely disposed flat surfaces of said heat sink are joined by curved segments, said segments elevating said lamp from the bottom of said cannister, thereby providing a circulating path for air currents.

References Cited UNITED STATES PATENTS 2,176,657 10/1939 Finch 257-250 2,735,636 2/1956 Snyder 3391l2X 2,935,549 5/1960 Woods 339-112X 3,001,097 9/1961 Smialek 339-144X RICHARD E. MOORE, Primary Examiner.

US. Cl X.R. 339-145 

